A.G. Barbosa de Lima

Advances in Building Technologies and Construction Materials 2016

CONSTRUCT-LFC, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, -ákurova 7/2077, 166 29 Prague 6, Czech Republic Department of Mechanical Engineering, Federal University of Campina Grande, Av. Apŕıgio Veloso, 882, 58429-900 Campina Grande, PB, Brazil

Moisture Transport Process in Vegetable Fiber Composites: Theory and Analysis for Technological Applications

This chapter provides theoretical and experimental information about water absorption in unsaturated polyester polymer composites reinforced with vegetable fibers. The use of raw materials from renewable sources, such as natural fibers, has shown great promise in a variety of engineering applications. Composites reinforced with natural fibers are sensitive to influences from environmental agents such as water and temperature. The organic nature of vegetable fibers is responsible for the higher moisture sensitivity of the mechanical properties of natural fiber reinforced composites when compared to synthetic fiber reinforced composites. Here, topics related to theory, experiments, mathematical modeling and numerical procedures, and technological applications for different natural fibers are presented and discussed in detail. Results of microscopy, water absorption kinetics, moisture content distribution, and area/volume relationships for unsaturated polyester composites reinforced with caroa and macambira vegetable fibers are shown and analyzed. The knowledge of moisture distribution allows the determination of areas that may show delamination problems (moisture induced degradation) due to the weakness of the fiber-matrix interface and consequently reduction in the composites mechanical properties.

Transient Diffusion in Arbitrary Shape Porous Bodies: Numerical Analysis Using Boundary-Fitted Coordinates

This chapter provides information about the diffusion phenomenon (heat and mass transfer) in porous materials such as definition, classification, modeling and experiments, with particular reference to capillary-porous body with arbitrary shape. A transient three-dimensional mathematical formulation written in boundary-fitted coordinates and all numerical formalism to discretize the diffusion equation by using the finite-volume method, including grid generation and numerical analysis of the computational solution are presented. Applications to food and ceramic industries have been done with success. An optimization technique has been presented to estimation of transport properties by comparison between numerical and experimental data.

Transport phenomena and drying of solids and particulate materials

Porous Materials Drying Model Based on the Thermodynamics of Irreversible Processes: Background and Application.- GBI Method: A Powerful Technique to Study Drying of Complex Shape Solids.- Grain Drying Simulation: Principles, Modeling and Applications.- Food Dehydration: Fundamentals, Modelling and Applications.- Convective Drying of Food: Foundation, Modeling and Applications.- Solid State Fermentation: Fundamentals and Application.- Drying of Fruits Pieces in Fixed and Spouted Bed.- Nutricional Enrichment of Waste from Mesquite Pods (Prosopolis juliflora) using Saccharomyces cerevisiae.- Evaluation of Cashew Apple Bagasse for Xylitol Production.

Cyclone: Their Characteristics and Drying Technological Applications

Cyclone is one of the most widely known device being extensively used to separate particles from a gas stream, and more recently as a modern drying technology (cyclonic dryer). In this sense, this chapter aim to briefly discuss disperse multiphase flow and heat and mass transfer theory in a cyclone as dryer, focusing principle of operation, design and selection, overall collection efficiency, particle–particle and fluid-particle interactions, particle residence time and, performance to moisture removal of moist particles. A transient three-dimensional mathematical modeling to predict fluid flow fields, particle trajectory, and gas-particle interactions (heat and mass transfer, dimensions variations and force effects) is presented and discussed. Application to sugar and alcohol industry (sugar-cane bagasse drying) has been done, and predicted results are compared with experimental data.

Intermittent Drying: Fundamentals, Modeling and Applications

This chapter focuses on the intermittent drying of wet porous bodies. Drying process was simulated assuming liquid diffusion as the sole mass transport mechanism and constant mass diffusion coefficient. Application has been done to ellipsoidal solids. The transient mass diffusion equation in a prolate spheroidal coordinate system was used to study the process in two-dimensional cases. Results are presented, changing the dimensionless tempering time, aspect ratio of the body and number of drying passes, by using the continuous drying process, drying rate, energy cost, drying time and quality of the product post-drying as comparison parameters.

Drying of Bioproducts: Quality and Energy Aspects

This chapter briefly focuses on the drying of wet bioproducts with particular reference to fruits, vegetables and grains. Different related topics in terms of drying foundations, dryer selection, product quality, energy savings, energy sources, energy efficiency, energy recovery, operating safety, environmental impact, and advanced drying techniques are presented and discussed. The study confirm drying as a highly energy-consuming process, one of the major source of pollutant emissions, and one dehydration technique that strongly affect product quality under different aspects such as color, flavor, appearance, aroma, losses of nutrients and vitamins, and many others physical, chemical, structural, and nutritional quality parameters.

Water Sorption of Vegetable Fiber Reinforced Polymer Composites

Despite the ever-growing worldwide interest in the use of lignocellulosic fibers as reinforcement in either thermoset or thermoplastic matrices, the use of these fibers to replace synthetic ones, is limited. The reasons for these limitations are associated with the vegetable fiber’s heterogeneity, lower compatibility to most polymers, inferior durability, flammability, poorer mechanical properties and higher moisture absorption when compared with synthetic fibers. Nevertheless, despite these drawbacks, vegetable fiber reinforced polymer composites are lighter in weight, more sustainable and can be used for non-structural products. Strategies to minimize these drawbacks include fiber and or matrix modification, the use of compatibilizers, fiber drying and the concomitant use of vegetable and synthetic fibers, for the production of hybrid composites, the latter being an unquestionable way to increment overall mechanical and thermal properties of these hybrid systems. Here we present data on the water sorption of polymer composites having thermoset and thermoplastic matrices as a function of vegetable fiber identity, content and hybridization with glass fibers. Our data indicates that, regardless if the matrix is a thermoset of a thermoplastic, water absorption tends to be relatively independent of vegetable fiber identity and to be significantly dependent of its content. Fiber drying prior to composite manufacturing and hybridization with glass fibers leads to lower overall water absorption and higher mechanical properties.

Water Absorption in Polymer Composites Reinforced with Vegetable Fiber Using Langmuir-Type Model: An Exact Mathematical Treatment

This work presents a theoretical study of the anomalous behavior of moisture transient diffusion in vegetable fiber-reinforced composites materials using Langmuir-type model. For obtain the analytical solution was used the Laplace transform technique. Results of the absorption kinetics and concentration distribution of water (free and trapped water molecules) within the material along the process are presented and analyzed. Predicted results compared to experimental data of average moisture content have shown that the model was effective for description of the phenomenon, allowing a better understanding about the effects of moisture migration mechanisms.

Transient Heat Transfer in a Packed-Bed Elliptic Cylindrical Reactor: A Finite-Volume Approach

This work aims to develop a transient three-dimensional mathematical model using the elliptic cylindrical coordinate system, to predict heat transfer in a elliptic cylindrical packed fixed bed reactor. The model considers variable thermo physical properties and a parabolic temperature profile at the fluid inlet. The governing equation is solved using the finite volume method. Results of temperature profile along the reactor are presented and discussed at different moments.It was verified that the maximum heat transfer rate inside the reactor occurs near the extreme region close to minor semi-axis of the ellipse; the higher temperatures at the reactor surface are also in this region, along the entire height of the bed; the steady-state regime is reached at t = 4.5 s of process, presenting after this time interval,small axial temperature gradients and high radial gradients along of the reactor bed; the parabolic temperature profile give to the bed a predominance of radial temperature gradients, and the radial porosity profile favours a higher heat transfer rate at reactor surface.